The high luminous efficiency, long life and mercury-free characteristics of LEDs have made it a trend to replace the fluorescent tubes with LED tubes. There are two main ways for this replacement application. One way is to completely remove the original fluorescent tube and ballast, and directly input the mains electricity to the LED tube. This method needs to modify the internal wiring of the lamps, additional labor cost is generated. The other way is only to replace the lamp tube. The mounted LED tube needs to be compatible with the original ballast. This kind of replacement is very simple and convenient, and a user can operate it himself without having to hire a professional person, which can eliminate the related labor cost.